So far depending upon an affected or diseased part of a body, a laser hand piece of a suitable focal length which emits the laser light in a predetermined direction must be selected. The prior art laser hand pieces comprise, in general, a shank into which is housed a laser light converging means or into which are housed a laser light converging means and a laser light reflecting means. The shank is securely attached to the leading end of a laser light transmission means and a plug which interconnects between the laser light transmission means and a laser light oscillator is securely attached to the rear end of the laser light transmission means. As a result, in order to change the function of a laser hand piece, the laser light transmission means as well as the plug which are associated with the shank must be also replaced. As a consequence, it is very cumbersome to change the function of a laser hand piece. Furthermore, each shank is provided with a laser light transmission means and a plug, so that the cost of the laser hand piece is expensive and the cost for repair and maintenance of the laser hand piece is also expensive. In addition, when a laser hand piece is used in the cases of surgical operations, there arises the problem that the laser hand piece must be sterilized or disinfected in a complicated manner.